#pragma GCC optimize("O3")
#pragma GCC target("avx2,bmi,bmi2,popcnt,lzcnt")
#include <bits/stdc++.h>
#define exoworldgd cin.tie(0)->sync_with_stdio(0),cout.tie(0)
using namespace std;
int press(string s);
const char c[] = {'A','B','X','Y'};
int ask(string s) {return press(s);}
int ask1(string s) {
int len = press(s+c[0]+s+c[1]);
int idx = 2*(len < s.length()+1);
len = press(s+c[idx]), idx += (len<s.length()+1);
return idx;
}
string guess_sequence(int n) {
string s;
int idx[4];
iota(idx,idx+4,0);
int id = ask1(s);
s += c[id], swap(idx[id],idx[3]);
for (int i = 0; i < n-2 ; i ++) {
string temp;
for (int j =0; j < 3; j++) temp += s+c[idx[0]]+c[idx[j]];
temp += c[idx[1]];
int len = ask(temp);
len == i+3 ? s += c[idx[0]] : (len== i+2 ? s += c[idx[1]] : s += c[idx[2]]);
}
if (n > 1) s += c[ask1(s)];
return s;
}
